It is known that prosthetic appendages, such as toes, thumbs, ears, eyes and the like, can be attached to a bone by using one of more attachment devices in the form of implants surgically positioned in recesses formed in the bone. One known system uses a type of implant having a threaded bore which is adapted to receive a threaded post of an abutment. The abutment in turn mounts the prosthesis. Although considerable success has been achieved with this system there is an inherent problem in that there is a certain space which must be provided between the male and female threads of a threaded system to which endotoxins and bacteria can find access.
This problem can be greatly diminished by using a locking or self holding taper arrangement for the implant bore and post member since a tighter fit is obtained. Such an arrangement is disclosed for dental applications in U.S. Pat. No. 4,738,623, the subject matter of which is incorporated herein by this reference. In recent years this system has come into wide use. In accordance with the patent, a dental implant of root member is surgically positioned within the mandibular of maxillary alveolar bone of a patient and, after healing, is fitted with a tooth-simulating prosthesis or crown. The root member is formed of biocompatible material, such as titanium, and is provided with multiple, outwardly extending fins to promote osseointegration with the alveolar bone. The implant is provided with a bore having a locking taper extending through the crestal end thereof. A permanent abutment member having a post portion, also formed with a locking taper, is mounted on the implant. The abutment member has an upstanding exterior surface adapted for mounting the prosthesis crown or denture and a basal portion having a spherical surface which extends through the gingiva and alveolar crest toward the implant.
Even though a tighter fit is obtained with a locking taper arrangement as described above, due to manufacturing tolerances it is possible for the taper of the post and the bore to be such that locking engagement occurs at the distal end of the post with the inner part of the bore thereby leaving a small annular crease available for endotoxins and/or bacteria cultures at the mouth of the implant. Due to the nature of the vascular supply of the mouth this phenomenon is not normally of great concern however, it is a significant concern where the application involves going through the epidermis.